TOTALS FOR FOOD STAMPS ARE A SHIFTING TARGET

By ROBERT PEAR, Special to the New York Times

Published: February 17, 1982

WASHINGTON, Feb. 16—
Are the food stamp rolls growing or shrinking? Do budget cuts exist only in the eyes of the beholder? Those questions have arisen as a result of a repetition by President Reagan. In his budget last year, Mr. Reagan said that one in 10 Americans were receiving food stamps. At his request, Congress then tightened the eligibility criteria. Agriculture Department officials predicted that 875,000 Americans would be cut from the program.

But when Mr. Reagan sent Congress his 1983 budget this month, he again reported that ''one out of 10 Americans now receives food stamps.'' And he asked Congress to make further reductions, expected to result in the removal of 2.8 million more people from the food stamp rolls.

Officials at the Office of Management and Budget said that the calculations for 1982 and 1983 were both based on a national population of 225 million but they emphasized that statements about ''one in 10 Americans'' were rough estimates. Estimate of 20.5 Million a Month

On the average, Agriculture Department officials say, there will be 20.5 million people participating in the food stamp program each month this year, although the total was as high as 21.7 million in November 1981, the most recent month for which statistics are available. The program is expected to cost nearly $11.1 billion this year.

What happened? Why is it so difficult to reduce the cost of Government benefit programs, as President Reagan wants to do? The answers are complex, and they are wrapped up in politics as well as budgetary arithmetic. Officials in the Reagan Administration and Congress spend countless hours trying to compute the potential savings from minor adjustments in the rules for benefit programs such as food stamps, Medicaid, railroad retirement and unemployment compensation.

The factors that complicate the calculations for food stamps affect other programs to some degree. But they are seen most vividly with food stamps because that is the only program offering benefits to all poor people, regardless of age, family composition or physical disability. They See Tie to Unemployment

The food stamp rolls, according to Agriculture Department officials, are acutely sensitive to the unemployment rate. As a rule of thumb, the officials figure that an increase of one percentage point in the unemployment rate adds 1.1 million people to the food stamp rolls.

Last March the Reagan Administration predicted that unemployment would average 7.7 percent from October through December 1981. Actually the average rate was 8.3 percent. The number of food stamp recipients was therefore at least 600,000 higher than expected, Agriculture Department officials estimate, because of higher unemployment.

In budget documents last year, the Reagan Administration said, ''Contrary to some popular suggestions, the growth in food stamp participation is not largely related to rising unemployment.'' It said that participation increased much faster than unemployment from 1978 to 1980.

However, Robert Greenstein, who was administrator of the Food and Nutrition Service in the last two years of the Carter Administration, said that there were other causes for the increase. For example, the requirement that people spend some of their own money to purchase food stamps was eliminated. He and other experts insisted that participation in the food stamp program was indeed tied closely to the jobless rate. Each Overflows Into the Other

Another factor is the interaction among social welfare programs. Last year Congress, at President Reagan's request, cut back benefits and eligibility in the main Federal-state welfare program, Aid to Families with Dependent Children. Families that lost these benefits became eligible for more food stamps, because food stamp allotments increase as a person's income decreases.

When the income of a food stamp recipient declines $1, he becomes eligible for 30 cents additional of food stamps. Cutbacks in unemployment insurance, manpower training and state welfare programs also tend to push up demand for food stamps, according to Agriculture Department officials.